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Biomedical subjects

J Y Chapelon

Publications and source records attributed to J Y Chapelon.

8 recordsLinked to original sources
PubMed1992

In vivo effects of high-intensity ultrasound on prostatic adenocarcinoma Dunning R3327.

High-intensity ultrasound has been used to treat Dunning R3327 prostatic adenocarcinoma implanted s.c. in Fischer Copenhagen rats. Focused ultrasound was generated with a 1-MHz transducer and energy was provided by a 7.5-kW power amplifier. Seventy-four rats were treated using two different sublines of Dunning tumor. Study 1 dealt with 49 rats with the Mat-Ly-Lu subline, treated with acoustic intensities ranging from 300 to 2750 W/cm2. Of the 49 rats in Study 1, 30 had complete tumor necrosis and 19 had no effect; of the 30 who had complete local tumor necrosis, 14 had local relapse, 9 had distance metastases to lung and nodes without local occurrence, and 7 remained free of tumor and were still alive 12 months after treatment. In Study 2, 25 rats with AT2 subline were treated with an intensity of 820 W/cm2. Similarly for Study 2, there was complete local tumor necrosis in 24 of 25 animals, with local regrowth in 7 of 24 and no recurrence of metastasis in the remaining 16 after a follow-up of 3 months. These results suggested that high-intensity focused ultrasound could be useful for the treatment of small localized cancerous tumors such as low-grade prostate carcinoma.

Adenocarcinoma↗
PubMed1992

Effects of high-energy focused ultrasound on kidney tissue in the rat and the dog.

In vivo tissue destruction was performed on 124 rat and 16 canine kidneys by focusing high-intensity ultrasound with a 1- and 2.25-MHz transducer. A precise tissue lesion was obtained in both models which varied in size according to the number of firings and the acoustic intensity. In the rat experiments, which were used to define the constants necessary to produce a localized tissue lesion at the focus of the transducer, the lesions obtained were either coagulating necrosis or a 'punched out' cavity which represented the threshold of tissue ablation. In the canine experiments, a kidney lesion was achieved in 10 animals (63%) extracorporally. These lesions were also histologically determined to be coagulation necrosis. These lesions are created by highly focused ultrasound and are caused most likely by a combination of cavitation and thermal effects, depending on the duration and frequency of the ultrasound bursts. Exact mechanism of this effect is explored as well as potential clinical applications in treating kidney, liver, and prostate tumors in humans.

Animals↗
PubMed1992

[Tumor ablation with focalized ultrasound. In vivo experiment with prostatic adenocarcinoma R3327 Mat-Ly-Lu].

Ultrasound can induce tissue lesions by a combination of thermal and mechanical effects related to the tissue absorption of the energy emitted at the focal point of the transducer. The effects of focused ultrasound were studied in vivo in Fisher/Copenhagen hybrid rats bearing Dunning R3327 experimental prostatic carcinoma. The experimental tumour was transplanted by subcutaneous injection into the abdomen of 20 mg of tumour tissue derived from the Mat-Ly-Lu strain. Treatment was performed under general anaesthesia. The animal, maintained in a sarcophage exposing the tumour, was immersed in degassed water ensuring the interface between the tumour and the 1 MHz transducer. The displacements of the transducer were guided by computerised ultrasound screening, allowing irradiation of the entire tumour. The energy was supplied by a 7.5 kW amplifier in the form of series of impulses of variable duration. 77 rats were treated and the tumour growth was compared to that of non-irradiated control rats. Comparative series demonstrated the following results: 1. Immediate tumour destruction was obtained with a very high acoustic intensity (9,000 Watts/cm2) and a brief exposure time. 2. A transient slowing of the tumour growth rate was observed for an acoustic intensity of between 3,500 and 5,500 Watts/cm2. 3. Partial or total necrosis of the tumour was obtained with intensities of between 300 and 2,750 Watts/cm2 and a long exposure time. Total tumour destruction was obtained in 30 of the 49 rats treated under these conditions. 14 animals developed a local recurrence, 9 animals did not develop a local recurrence but developed metastases and 7 animals obtained long-term survival without local recurrence or metastasis. Under certain experimental conditions, focused ultrasound, without any adjuvant treatment, was able to destroy the Dunning R3327 Mat-Ly-Lu strain experimental tumour and, in certain cases, induced complete cure of this experimental cancer.

Animals↗
PubMed1991

Cytotoxic effects of acoustic cavitation on HT-29 cells and a rat peritoneal carcinomatosis in vitro.

Damage to cells and tissues exposed to shock waves (SWs) is thought to be secondary to cavitation phenomena involving the collapse of gas bubbles in a fluid. Using HT-29 cells and DHDK12PROb tumors, we tried to enhance SW-related damage by the simultaneous administration of gas microbubbles. Bubbles resulted from a mixture of air and gelatin (HT-29 cells) or from a carbonated NaCl solution (tumors). HT-29 cells in suspension received either SW (50, 250, or 1000 SWs) alone or in association with bubbles. Trypan blue-negative cells decreased as the number of SWs increased. Exposure to SWs and bubbles resulted in not only an increased but also a delayed mortality as compared to SWs only. One thousand SWs with bubbles induced a complete inhibition of cell growth, with cytoplasmic vacuolae, ruptured membranes, and abnormal nuclear shape and chromatin. Exponential and confluent cells exhibited a similar mortality and growth. DHDK12PROb tumors received either SWs only (50, 100, 250, 500, or 1000 SWs) or SWs with bubbles in vitro. Thymidine incorporation was significantly lower after exposure to SWs with bubbles as compared with controls and SWs only; it was nil by 1000 SWs with bubbles. Histopathological features of tumors exposed to SWs with bubbles included erosion and hemorrhage, disorganized structure, pyknotic nuclei, and cytoplasmic vacuolae. We conclude that cavitation, as produced by a combination of SWs and gas microbubbles, can achieve bioeffects which are relevant to cancer therapy.

Animals↗
PubMed1991

[Tissue ablation by focused ultrasound].

Tissue lesions can be induced at the focal point of highly focused transducers with a frequency of 1 and 2.25 MHz for exposure times of less than 1 second. The energy generated by a high power amplifier (7.5 kilowatts effective at 1 MHz) is delivered in the form of series of impulses lasting between 10 and 1,000 milliseconds. The experimentation was conducted in the rat kidney (the left kidney, normally supplied by its vascular pedicle, was exteriorised during ultrasound treatment and then returned to the abdomen). The animal was sacrificed 3 days later and the lesions were studied by serial histological sections. 248 ultrasound shots were performed between January and September 1990. They allowed the definition of the time and intensity constants necessary to induce total destruction of the renal tissue at the focal point. Depending on the energy delivered, an elliptical cavity with a mean height of 1.2 to 4.6 mm and a mean diameter of 0.6 to 3 mm is observed at the focal point after a single shot. No cell structures were visible in the cavities and, in general, the cavity was prolonged by a cone-shaped region of coagulated necrosis with an inferior base. The mechanism responsible for this focused ultrasonic tissue destruction (FUTD) involves a variable combination of thermal and mechanical effects which depends on the ultrasound intensity delivered at the focal point of the transducer.

Amplifiers, Electronic↗
PubMed1991

Hepatic lesions in the rabbit induced by acoustic cavitation.

Tissue damage during shock-wave lithotripsy is presumably secondary to cavitation phenomena involving the collapsus of gas bubbles in a fluid. To enhance shock-wave-related hepatic lesions, intravascular gas microbubbles were administered. Three groups of eight rabbits each received either 500 shock waves focused on the right hepatic lobe (group 1), gas microbubbles as a mixture of 50 cm3 of air with 50 cm3 of gelatin infused through an arterial catheter (group 2), or 500 shock waves and gas microbubbles simultaneously (group 3). In group 1, two animals had two to three subcapsular hepatic hematomas (diameter, less than 5 mm) and five had one to five intraparenchymal hematomas (less than 1 mm). In group 2, a moderate liver congestion was observed in three animals. In group 3, all animals had numerous subcapsular and intraperenchymal hematomas (2-30 mm). The hematomas were centered around the portal spaces, associated with lacunae (0.5-5 mm in diameter). Hematomas were also present on the anterior wall of intraabdominal organs. It was concluded that intravascular infusion of gas microbubbles into the path of a shock-wave generator dramatically enhances tissue damage. This technique, potentially useful in the treatment of hepatic tumors, needs refinement to confine lesions in a more uniform pattern to the targeted parenchyma.

Animals↗
PubMed1976

Detailed description of an implantable directional Doppler flowmeter.

A Doppler flowmeter and the necessary modifications for implantation are described in detail. Since only part of the electronics was implanted a phase-locked loop had to be introduced in order to keep the flow measurement directional. The proper working of the apparatus is demonstrated in vitro and in vivo. As an example the result of flow studies in the aorta and the pulmonary artery after homotransplantation of the lung in dogs are given.

Animals↗